In large skillet, melt butter over medium-high heat. Add frozen peas and carrots and frozen onions; cook 3-4 minutes or until thawed. Add chicken; cook 2-3 minutes or until heated through. Sprinkle with flour; cook 1 minute, stirring constantly. Stir in chicken broth and bring to a simmer. Cook 6-8 minutes until thick, stirring often. Stir in 1 tablespoon parsley and pepper. Let cool 5 minutes.